New Long-Lasting Malaria Vaccine Approach Identified

Malaria vaccines lose their effectiveness in the short term

A new vaccine approach to protecting people from malaria is offering promising results against the parasite that impacted 219 million people, leading to 435,000 deaths, during 2017.

About 1,700 cases of malaria are diagnosed in the United States each year, says the World Health Organization (WHO).

Malaria is a serious and sometimes fatal disease caused by Plasmodium parasites, which are spread to humans through mosquito bites.

The search for an effective, long-lasting malaria vaccine has been challenging.

This new vaccine method reduced the malaria-causing parasite's release from the liver and into the blood of infected rhesus macaques by 75 to 80 percent, reports a paper published in the journal PLOS ONE.

This approach uses a cytomegalovirus (CMV) based platform that's already being used in vaccines being developed to battle HIV and tuberculosis.

Most vaccines are designed to encourage the human body to respond to invading, disease-causing pathogens by creating antibodies that disable those pathogens.

This vaccine strategy takes a different approach by using a weakened form of a common herpes virus - CMV - that infects most people without causing disease.

Klaus Früh, Ph.D., of Oregon Health & Science University (OHSU)'s Vaccine & Gene Therapy Institute and a professor of molecular and cellular biosciences at the OHSU School of Medicine and his colleagues weave tiny bits of their target pathogen into CMV.

These OHSU researchers developed 2 different versions of their CMV-based malaria vaccine while using 4 different proteins made by the Plasmodium parasite.

The resulting vaccines delayed the parasite's appearance in the blood of 16 infected and vaccinated rhesus macaques by eliminating between 75 and 80 percent of parasites from the liver.

One year later, the vaccinated nonhuman primates still had immunity against malaria, while eight control animals that weren't vaccinated did not.

Previous studies have shown this approach enables vaccinated nonhuman primates to develop and maintain a high state of immunity years later.

"The problem with most vaccines is that their effectiveness is often short-lived," said the study's lead author, Dr. Klaus Früh, in a press release.

"With further research and development, it could offer a lifetime of protection against malaria."

The World Health Organization is using one vaccine - known as RTS,S/AS01 or by its brand name, Mosquirix - as part of new, routine vaccination programs in three African countries.

But, RTS,S has been shown to only reduce malaria transmission in children - in whom malaria is most often fatal - by 39 percent 4 years after it was administered.

Its efficacy was further reduced to 4.4 percent 7 years afterward.

In an effort to make their vaccine 100 percent protective against malaria, the research team will evaluate 15 different Plasmodium-made proteins for the vaccine.

They will also examine combining their CMV-based vaccine with other experimental vaccines or the existing RTS,S vaccine.

This CMV vaccine platform has been licensed by Vir Biotechnology, Inc., of San Francisco, which plans to lead a human clinical trial for a CMV-based HIV vaccine in the next 12-18 months.

OHSU and Drs. Picker, Hansen, and Früh have a significant financial interest in VIR Biotechnology Inc.

The study was a collaboration between OHSU, the Naval Medical Research Center, National Institutes of Health and Fred Hutchinson Cancer Research Center.

This research was supported by the Military Infectious Diseases Research Program (grant F0351_12_NM) and the National Institutes of Health (grants R21AI103498, RO1AI059457, P511OD011092, R24 RR016001, HHSN 2722000900037C)

The World Malaria Report, published annually, provides a comprehensive update on global and regional malaria data and trends.

The latest World Malaria Report, released on 19 November 2018, tracks investments in malaria programmes and research as well as progress across all intervention areas: prevention, diagnosis, treatment, and surveillance.